THE El Nino that has often been the bane of the Indian monsoon is also the reason for the unusually warm winter season this year. Average temperatures across the country, except in Jammu and Kashmir and some adjoining areas, are about 4 to 5 degrees above normal and scientists say the prevailing El Nino in the Pacific Ocean must be held responsible.

El Nino refers to a condition in the equatorial Pacific Ocean, off the coast of Ecuador and Peru in South America, in which sea surface temperatures become unusually warm. The warmer ocean temperatures are the reason behind several weather events worldwide, and are known to suppress the Indian monsoon as well.

Arvind Kumar Srivastava, former head of the National Climate Centre in Pune, said it is not unusual to find winter temperature following an El Nino event to be slightly “milder” than normal. He said the 2009-2010 winter, which followed an El Nino event, was also not very cold. “But the current El Nino has been very strong and prolonged. So its impact is being felt in a more forceful manner,” said Srivastava, now the director of the meteorological centre in Jaipur.

In fact, the prevailing El Nino, which is likely to stretch till early summer this year, is one of the strongest in recent times. The January 4 ‘El Nino Advisory’ from the Climate Prediction System of the National Oceanic and Atmospheric Administration of the United States says the expectation was that the current El Nino event “will rank among the three strongest episodes” since 1950.

It has already resulted in one of the lowest monsoon rainfalls in recent years this season. And now it could be resulting in a warmer winter. J Srinivasan of the Divecha Centre for Climate Change at the Indian Institute of Science, Bangalore, said the strength of El Nino could be accounting for about 1 to 2 degree rise over the normal temperatures at this time of the year.

There are other, more local, factors as well that are contributing to the unusually high temperatures this winter. Primary amongst them is the lack of rain. The last week of December and first week of January generally see rainfall through most of north India, including Delhi. But this year there has been no rain in this period in most parts of the country.

In the last week of December, the country as a whole received rainfall that was 86 per cent below normal. Kerala, Tamil Nadu, parts of Andhra Pradesh, Orissa and Jammu and Kashmir received some rainfall but rest of the country was completely dry.

Scientists blame the prevailing, unusual, atmospheric conditions for this. Rain at this time, at least in northern India, is brought by the ‘westerlies’, a system of wind that moves in the mid-latitudes, 30 to 60 degrees, in northern hemisphere from the west to east direction. These winds move slightly southwards during this time and flow through most of northern and central India.

“But this year, they have remained north of their usual position during this time and as such their zone of influence has only been parts of Jammu and Kashmir, Punjab and Himachal Pradesh where we have seen a little bit of rain,” said L S Rathore, director general of the Indian Meteorological Department.